Randomized Controlled Trial of Aerobic Exercise on Insulin and Insulin-like Growth Factors in Breast Cancer Survivors: The Yale Exercise and Survivorship Study

Abstract

Background: High insulin and insulin-like growth factor-I (IGF-I) levels may be associated with an increased breast cancer risk and/or death. Given the need to identify modifiable factors that decrease insulin, IGF-I, and breast cancer risk and death, we investigated the effects of a 6-month randomized controlled aerobic exercise intervention versus usual care on fasting insulin, IGF-I, and its binding protein (IGFBP-3) in postmenopausal breast cancer survivors. Methods: Seventy-five postmenopausal breast cancer survivors were identified from the Yale-New Haven Hospital Tumor Registry and randomly assigned to an exercise (n = 37) or usual care (n = 38) group. The exercise group participated in 150 minutes per week of moderate-intensity aerobic exercise. The usual care group was instructed to maintain their current physical activity level. A fasting blood sample was collected on

Effects of 8 Weeks of Resistance Training and IGF-1 Injection on Biochemical Markers of Cancer and Colorectal Structures in Rats

“…We found that two months of exercise training decreased circulatory IGF-1, when compared with the control group. This is in line with the results of previous studies (7,16,17,26). Evidence indicates that reduction of serum IGF-1 by lifestyle modification reduces the number of cancer cells, slows tumor progression and increases apoptosis in tumor cells (3, 7).…”

“…However, the exact mechanism of this phenomenon is not clear. Several biological mechanisms could explain exercise training-induced decrease in IGF-1, including increased post-receptor insulin signalling, increased glucose transporter protein and mRNA, decreased release and increased clearance of free fatty acids, and increased muscle glucose delivery (17,27). In addition, decrease in pro-inflammatory cytokines (28) and increase in skeletal muscle IGF-1R density and activation may be other potential mechanisms for the exercise-induced reduction in systemic levels of IGF-1 (1).…”

“…Some studies have reported that acute resistance and endurance exercise increase serum IGF-1 concentrations but do not affect serum IGFBP-3 levels (2, 10, 11). Although several studies have examined changes in circulating level of IGF-1 and IGFBP-3 in response to exercise training, the results of such studies have been inconsistent (12)(13)(14)(15)(16)(17)(18)(19). Moreover, overexpression of IGF-1 and IGFBP-3 is thought to increase tumor size in colorectal cancer (9, 20).…”

Effects of a combined strength and high-intensity aerobic exercise program in breast cancer survivors: A pilot study

“…The authors identified significant differences between the two groups (−10.9%). Irwin et al 7 reported a 3% decrease in IGF-I plasma levels in the exercise group and a 5.5% increase in the control group, representing a clinically significant difference (p = 0.089). The exercise program in that study comprised moderate-intensity aerobic exercise for 150 min per week for 24 weeks.…”

“…6 Several studies have demonstrated a relationship between high concentrations of IGF-I and the risk of recurrence and death in BCSs. 7 There is now ample epidemiological and experimental evidence for the role played by physical activity in the rehabilitation of female BCSs. Meta-analyses and systematic reviews of randomized clinical trials have confirmed the positive effects of physical exercise on biological and cardiopulmonary function and the reduction of sex hormones, body fat mass, insulin, IGFs, adipocytokines, and mammographic density, as well as increased immune function and improved antioxidant defense systems and QOL in BCSs.…”